Method of producing a reactive coating by after-glow plasma polymerization

ABSTRACT

The present invention describes coated articles and methods for preparing such articles, wherein the primary coating comprises a plasma-induced polymer carrying reactive groups. The invention further relates to the reaction of said primary coatings carrying reactive groups with monomeric, oligomeric or macromolecular compounds of synthetic, semisynthetic or biological origin to provide hybrid-type coated articles (secondary coatings).

The present invention relates to coated articles wherein the primarycoating comprises a polymer carrying reactive groups. The coating iscovalently linked to the surface of the article and exhibits acontrolled degree of crosslinking. The invention further relates to thereaction of said primary coatings carrying reactive groups withmonomeric, oligomeric or macromolecular compounds of synthetic,semisynthetic or biological origin to provide hybrid-type coatedarticles and to such articles which exhibit desirable characteristicsregarding adherence to the substrate, reactivity, lubricity, durability,biocompatibility, (bio)affinity, (bio)activity, permeability,permselectivity for gases, liquids and solutions, and wettability byaqueous solutions, such as human body fluids. More particularly, thepresent invention relates to an article, such as a biomedical materialor article, especially ophthalmic devices and implants such asartificial corneas, intraocular lenses and contact lenses, including anextended-wear contact lens which is at least partially coated. Thearticles are obtainable by after-glow plasma-induced polymerization of apolymerizable unsaturated compound having reactive groups, preferablypolymerizable vinyl or isopropenyl compounds carrying isocyanato,isothiocyanato, glycidyl, anhydride, azlactone or lactone groups underspecific plasma conditions. The invention further relates to sucharticles carrying a laminate coating obtainable by reacting saidreactive groups with a monomeric, oligomeric or macromolecular compoundof synthetic, semisynthetic or biological origin.

The provision of a coating on a substrate may generally be desirable fora variety of reasons including protection of the substrate and provisionof desirable surface characteristics which the substrate material doesnot exhibit to the required degree. In the case of biomedical devices,such as ophthalmic devices, e.g. contact lenses it is desirable to havesurfaces which are readily wettable by an aqueous liquid such as tearfluid and are capable to retain an aqueous fluid layer which preventseye irritation and is beneficial for the easy movement of the contactlens on the eye which in turn is important for the comfort of thewearer. The sliding motion of the contact lens is facilitated by thepresence of a continuous layer of tear fluid on the contact lens, alayer which lubricates the tissue/lens interface. Additionally, theadhesiveness towards proteins, lipids, minerals, cell debris and otherspoilations or micro-organisms and the permeability and stabilitycharacteristics of the surface of the contact lens having a coatingthereon are of great importance. The permeability of the lens materialfor gases, water and ions which is required especially in the case ofextended wear contact lenses must not be impaired by the coating whichis provided in order to impart hydrophilicity to the surface. Thecoating should exhibit thermal, oxidative and hydrolytic stability aswell as resistance to formation of deposits from tear components.Moreover, delamination caused by mechanical stress should not happen. Itis of particular advantage the coated article can be sterilized byautoclaving without affecting the uniformity, the thickness and theproperties of the coating.

Materials with wettable and biocompatible surfaces are highly desirablefor many applications. The wettability of materials is stronglydependent on topography, morphology and on the chemical composition ofthe material surface. In particular, the ability of the surface to holda continuous layer of an aqueous solution, such as tear fluid for aprolonged period or time (>10 seconds), is affected by the compositionof the material surface. Known attempts to solve the wettability problemin the ophthalmic field include methods for the activation of a devicesurface. The methods being generic, so that the surface of any materialwith suitable bulk properties can be converted to be receptive for thecovalent immobilization of a coating which is highly retentious foraqueous layers.

A number of surface treatment techniques for polymeric materials areknown in the art. Chemical Vapor Depostion (CVD), Corona discharge,ozone treatment, flame treatment, acid etching, and a number of othermethods intended to achieve chemical modification of the surface. Amongthe disadvantages of these techniques are the use of elevatedtemperatures or the use of hazardous chemicals, the often excessivedepth of treatment, non-uniformity of treatment at a microscopic level,and often severe etching and pitting that leads to changes in surfacetopography. The depth of treatment is important because with clearmaterials such as those required for lenses the optical clarity andsurface smoothness become affected after an excessively harsh treatment.Moreover, surfaces thus treated usually contain complex mixtures ofpolar groups of sometimes limited stability and are often highlycrosslinked which considerably affects the overall permeabilitycharacteristics.

Treatment of polymeric surfaces by gas plasmas provides the advantagesof very low treatment depth, and high uniformity on a microscopic scale.A gas plasma can for example be generated by glow discharge in a gasatmosphere at reduced pressure (“vacuum”). It creates a stable,partially ionized gas that may be utilized for effecting reactions onthe surface of the substrate because the gas plasma environmentactivates even chemical compounds that are unreactive under normalconditions. The treatment intensity at the surface is generallyrelatively high, and yet the penetration depth of gas plasma treatmentis very low, of the order of 5 to 50 nanometers, at a treatmentintensity sufficient for useful surface modification. Surface topographyand optical clarity do not change unless exposure to the plasma isperformed at high energy levels or for periods of time much exceedingthe time required for achieving the desired chemical modification of thesurface. Glow discharge plasma reactions therefore result insignificantly less alteration of the properties of the bulk material ascompared to the alternative treatment technologies described above.

Gas plasma techniques can have two types of outcomes. In the first,commonly called plasma surface treatment, the surface of a polymericmaterial to be treated (“the substrate”) is subjected to a plasmaestablished in one or more inorganic vapors or some select organicvapors, and the plasma treatment causes the replacement of some of theoriginal chemical groups on a polymer surface by other, novel groupswhich are contributed from the plasma gas. For instance, the plasmasurface treatment of polytetra-fluoroethylene in an ammonia plasma leadsto the abstraction of some of the surface fluorine atoms by C—F bondbreakage and the incorporation into the modified surface layer of aminegroups by C—N bond formation. Plasma surface treatment in an appropriatevapor such as ammonia, oxygen, carbon dioxide, or water vapor, cantherefore be used to place on the surface of any polymeric materialreactive chemical groups, such as amine, carboxyl, or hydroxyl, suitablefor the subsequent covalent immobilization of various molecules. Theoverall outcome of this technique is a surface functionalization of asubstrate material.

The second type of plasma technique is commonly called plasmapolymerization and occurs when a discharge is struck in most organicvapors. In contrast to plasma surface treatment, in which less than amonolayer of new material is added, the technique of plasmapolymerization leads to the formation of film coatings which can be upto several micrometers thick and can completely mask the substrate.

Plasma polymers are usually covalently bound to the underlyingsubstrate. The covalent attachment of the plasma coating to the bulkmaterial ensures that the plasma polymer does not detach. Furthermore,common plasma polymers are usually highly crosslinked and do not containleachable low molecular weight fragments which might migrate into bodytissue or fluids.

By appropriate choice of the monomer vapor and the plasma conditions,plasma polymer coatings can be fabricated to contain specific,chemically reactive groups which are also suitable for the subsequentchemical attachment of various molecules to the surface. Thus, WO94/06485 discloses activation of the surface of a polymeric materialwhich does not inherently carry suitable reactive groups by plasmasurface treatment, plasma polymerization, or plasma polymerizationfollowed by a subsequent plasma surface treatment. In this way, acomposite material, especially a biomedical device, e.g. an ophthalmicdevice, such as a contact lens can be provided having one or morewettable surfaces capable of holding a continuous layer of aqueous fluidthereon, wherein the composite comprises a carbohydrate which iscovalently bound by a hydrolytically stable bond to a plasma surfaceprepared on the base material.

JP-A-62/032884 discloses a method of immobilizing physiologically activesubstances comprising applying a plasma to the inner wall of a test tubefilled with monomer gas atmosphere of an aldehyde compound or adiisocyanate compound to form aldehyde groups or isocyanate groups onthe inner wall face of the test tube, and reacting amino groups of aphysiologically active substance (such as an enzyme) with thesefunctional groups to immobilize the active substance onto the inner wallface. According to the general teachings in plasma chemistry, adiisocyanate under plasma conditions can only form a polymer underfragmentation and recombination processes. Therefore, only a low contentof intact OCN-groups is expected in said disclosure.

Plasma polymerization as used in the prior art mentioned above is amethod wherein the substrate may be located within the plasma zone (socalled “in glow”) or alternatively outside (below) the plasma zone(“after glow”, downstream or remote plasma) and the monomer(s) as wellas the plasma gas stream (e.g. H₂, He, Ar) are introduced into theplasma zone.

While polymeric coatings prepared by this so-called “in-glow” plasmapolymerization may have suitable surface properties they do not consistof chains with regular repeating units but tend to form an irregularthree-dimensional crosslinked network; see A. P. Ameen et al., Polymer,Vol. 35 (1994) p. 4382. Organic compounds used as monomers are usuallyheavily fragmented by the plasma and form a complex mixture of variousions, atoms, radicals and other highly activated species. Susceptiblegroups, such as isocyanates, esters, anhydrides, epoxides and the likeare largely decomposed. Thus, the polymers deposited onto the substraterepresent complex, rather undefined structures formed by a multitude ofrecombination processes among the variety of fragments. As a result,functional coatings made by “in-glow” plasma polymerization usuallyexhibit a larger variety of O- and N-containing reactive groups.Moreover electrons and high energy photons derived from the aforesaidprocesses can further affect the structure and the composition of thecoatings. These coatings do not possess a highly regular arrangement ofunaltered monomer residues which is desirable in view of thepermeability characteristics required in case of coatings for biomedicaldevices like contact lenses. A further problem encountered with thein-glow plasma polymerization process is that the deposition of thecoating is usually accompanied by a simultaneous competitive surfaceerosion process caused by the bombardment by the highly activatedmolecule fragments. As a result of the primary and secondary reactionssuch plasma coatings usually are heavily restricted in theirpermeability behaviour due to high cross-linking.

Modifications of the “in-glow” plasma polymerization process are“post-plasma” poly-merization or -coating or -deposition which is alsocalled “plasma-induced” polymerization or -coating or -deposition, and“after-glow” plasma-induced polymerization or -coating or -depositionwhich is also called “downstream” plasma-induced polymerization or-coating or -deposition, or “remote” plasma-induced polymerization or-coating or -deposition.

For “post-plasma” polymerization the surface of a substrate is treatedfirst with a non-polymerizable plasma gas (e.g. H₂, He or Ar) and thenin a subsequent step the surface thus activated is exposed to a monomerwith the plasma power having been switched off. The activation resultsin the plasma-induced formation of radicals on the surface which in thesubsequent step initiate the polymerization of the monomer thereon.

While post-plasma polymerization is a process in which the monomer to bepolymerized is not exposed to the high energy plasma and is thus notsuffering activation and/or fragmentation, the method is of limitateduse because of the low deposition rates.

In contrast to the post-plasma polymerisation process in whichpolymerization is carried out on the activated substrate after theplasma power has been switched off “after-glow” plasma-inducedpolymerization is a process in which polymerization is effected in thepresence of the plasma but wherein the substrate as well as the inletfor the monomer feed are located outside of (below) the plasma zone.Fragmentation of the monomer molecules can be largely avoided in thisway as the monomer does not pass the zone of the highly reactive plasmagases. With this process the structure of the polymer deposit can becontrolled within certain limits, undesired surface erosion ofsusceptible substrates can be avoided and the formation of the polymerdeposit is predominantly based on radical reactions.

It is an object of the present invention to provide articles having apolymeric primary coating which exhibits excellent adherence to thesubstrate and contains a rather high content of reactive groups, whichgroups are capable of undergoing fast and efficient addition reactionseven in aqueous environments and which are obtained by plasma-inducedpolymerization of a polymerizable unsaturated compound carrying saidreactive groups. If desired, the polymerizable unsaturated compoundcarrying said reactive group might be blended with one or morenon-reactive polymerizable unsaturated compounds or with unsaturatedcompounds carrying another type of functionality. Such blends mighttypically contain up to 60 weight %, preferably up to 20 wt. % and morepreferably up to 10 wt. % of non-reactive polymerizable usaturatedcompounds, but unblended are most preferred. The polymer chains of thecoating while exhibiting controlled crosslinking are composed to a largeextent of repeating units which are identical in structure to therepeating units obtained by non-plasma radical polymerization of thesaid polymerizable unsaturated compound.

The term “reactive groups” denotes within the present invention anisocyanato, isothiocyanato, epoxy, anhydride, azlactone or a lactonegroup, which is capable of undergoing typically an addition reaction,with a monomeric, oligomeric or macromolecular compound of synthetic,semisynthetic or biological origin, to form the final coating. A highlypreferred reactive group is the isocyanato group.

It is a further object of the present invention to provide primarycoatings of the above mentioned type which may be applied to a widevariety of substrates including organic polymers and inorganic materialssuch as metals, metal oxides, ceramic materials, glass, minerals andcarbon including graphite, or composites of these materials. Prior tosaid coating, said materials might be molded or shaped in many differentways, for example as nano- or microparticles, fibres, films, membranes,(micro)capsules, granules, (micro)beads, rods, sheets, hollow fibres,tubules, pipes, electrodes, (micro)chips, optical fibres, wave guides,valves and the like.

Another object of the invention is to provide primary and secondarycoatings to porous substrates without destroying their permeationcharacteristics.

It is a more specific object of the invention to provide primary andsecondary coatings of the above-mentioned type on a biomedical materialor article, especially an ophthalmic implant or a contact lens, mostspecifically an artificial cornea, an intraocular lens or an extendedwear contact lens which coating excels by good adherence to thesubstrate and superior biocompatibility, exhibits good permeability foroxygen, carbon dioxide, proteins, lipids, water and ions, highwettability, wear resistance, stability towards tear liquid anddeposition of proteins, lipids, mucins and salts and shows excellentcomfort for the wearer on continuous wearing, preferably of more than 6days and 6 nights.

It is a further object of the invention to provide a method forpreparing articles having a primary polymeric coating which exhibitsexcellent adherence to the substrate, has a structure of the repeatingunits as mentioned above and carries reactive groups on the surface in asimple and reliable one-step-process.

It is a further object to provide articles having a hybrid-type coatingobtainable by reacting the reactive groups comprised in the primarycoating with a monomeric, oligomeric or macromolecular compound ofsynthetic, semisynthetic or biological origin. Said hybrid-type coatingsexhibit outstanding thermal, oxidative and hydrolytic stability andresistance to delamination from the substrate caused by mechanicalstress, desirable permeation characteristics for liquids, gases, ions,nutrients and low molecular weight compounds while having controlledpermeability for high molecular weight biocomponents, such as proteins,glycoproteins and lipids.

The term “hybrid-type coating” relates within the terms of the presentinvention to a primary coating with the provisio that the reactivegroups have been modified to an unreactive moiety. In more detail, thehybrid-type coating might either represent a real layer by layer coatingor it might represent a primary coating with an additionalmono-molecular layer only. Accordingly, this modification might beeither effected with the above mentioned monomeric, oligomeric ormacromolecular compound of synthetic, semisynthetic or biologicalorigin, or it might be effected by any addition reaction ofsubstanatially any suitable molecule, such as addition of water,ammonia, C₁-C₇ alkanol, e.g. methanol, C₁-C₇ aminoalkane, e.g.methylamine, propylene glycol, glycerol, amino acid, carbohydrate or thelike.

Another more specific object of the invention is the provision of abiomedical material or article as mentioned above having a hybrid-typecoating as mentioned in the preceding paragraph which also has excellentwettability by aqueous solutions such as tear fluid, and provides forexample on a contact lens a tear film break up time of >10 seconds.

Another object is an article, in particular a biomedical orbioanalytical device having a hybrid-type coating as mentioned, whichprovides specific (bio)affinity or (bio)activity properties to thedevice. Examples of biomaterials forming the outer layer of thehybrid-type coating, obtained by reacting with the reactive primarycoating are:

Carbohydrates, oligosaccharides, polysaccharides, sugars, cyclodextrins,heparin, dextrans and glycoaminoglycans;

Peptides or proteins such as cell adhesion and antiadhesion factors,cell growth factors, enzymes, coenzymes, receptor proteins, lectins,antibodies, antigenes;

Glycopeptides, glycoproteins and lipoproteins, such as mucins andimmunoglobulins;

Phospholipids, glycolipids and lipoproteins, such as sphingolipids;

Nucleotides; such as DNA- or RNA-oligonucleotides;

Affinity species, which are capable of attracting, assembling and/ortemporarily binding specific molecular species, e.g. through a lock/key,host/guest and otherwise complementary interaction or complex formation(examples of such molecular species are biotin/avidin,cyclodextrin/host, antibody/antigen, enzyme/substrate/inhibitor,DNA/DNA, DNA/RNA, lectin/carbohydrate, drug/receptor protein etc.); and

Any of the above mentioned biomaterials which carries a specific labellike a fluorescent dye (FITC), colloidal gold, radio lablels, peroxidaseand the like, thus making the coated surface suitable for analytical anddiagnostic techniques.

The invention also relates to a device which contains an article coatedaccording to the above described technology. Examples of such a deviceare an ophthalmic device such as a contact lens, an intraocular lens oran artificial cornea; an artificial organ such as liver, pancreas,kidney or heart; drug delivery systems such as (micro)capsules,(micro)beads and transdermal membranes or a drug targeting system suchas tumor targeting or brain targeting; a bioanalytical system, affinitycarrier or a permselective membrane; prostheses and surgical repair orimplant materials and devices such as vascular grafts, bone repairs,nerve repairs, dental repairs or catheters.

These objects could be achieved on the basis of the finding, thatprimary coatings having a variety of desirable characteristics asmentioned above can be produced by plasma-induced polymerization of apolymerizable unsaturated compound carrying reactive groups on asubstrate in the after-glow zone of a plasma apparatus underspecifically controlled conditions including the distance of substrateand monomer inlet to the plasma zone.

Within the terms of the present invention, a polymerizable unsaturatedcompound carrying reactive groups is understood to represent a monomer,a comonomer, a polymer or a copolymer, which carries an unsaturatedmoiety such as vinyl or isopropenyl as well as a reactive group.

A subject matter of the present invention is thus an article comprisinga substrate with a primary polymeric coating carrying reactive groupspredominantly on its surface, wherein said polymeric coating comprisesrepeating units derived from a polymerizable unsaturated compoundcarrying reactive groups, wherein in said coating the concentration ofsaid reactive groups is, based on spin label determination by ESRspectroscopy, in a range of 0.2-20·10⁻⁹ Mol spin/cm², preferably in arange of 0.5-15·10⁻⁹ Mol spin/cm² and more preferably in a range of2-12·10⁻⁹ Mol spin/cm².

A preferred aspect of the invention relates to articles, wherein saidprimary polymeric coating might additionally comprise repeating unitsderived from one or more polymerizable unsaturated compounds notcarrying reactive groups.

Another preferred aspect of the invention relates to articles, whereinsaid primary polymeric coating comprises repeating units derived fromone or more polymerizable unsaturated compounds carrying reactivegroups.

In a further preferred aspect, the invention relates to articles,wherein 30% to 98%, preferably 50%-90% and more preferably 60% -80% ofthe repeating units are identical in structure to those repeating unitsobtained by non-plasma radical polymerization of said unsaturatedcompounds and wherein 2% to 70%, preferably 10% to 50% and morepreferably 20 to 40% of the repeating units represent sites ofcross-linkage and/or covalent bonding to the substrate.

Typically, a primary coating according to the present invention exhibitsa thickness of about 0.001-10 μm. A spin label determination experimentby ESR typically pertains to the three-dimensional concentration ofreactive groups, for example reactive groups per cubic centimeter (cm³).Consequently, the concentration of reactive groups, as determined byESR, reflects the total amount of such groups for a volume underlying anarea of e.g. one square centimeter (1 cm²). For very thin coatings, thisvolume corresponds almost to the two-dimensional area. Consequently, forvery thin primary coatings, the concentration of reactive groupsapproximately reflects the concentration of reactive groups on thesurface. For instance, in primary coatings having a thickness of 1-10nm, the number of reactive groups is typically in the order of 0.01 to 5reactive groups per square nanometer, and is typically depending on thenature of the monomers used.

The term primary coating relates to a polymeric coating comprisingreactive groups.

The thickness of such a primary coating is typically in the range of0.001-10 μm, preferably in the range of 0.01-1 μm and more preferably inthe range of 0.03-0.2 μm.

According to the invention the adherence of the coating to the substrateand the degree of crosslinking of the polymeric coating are such thatthe hybrid-type coating obtained after reaction of the reactive groupswith a suitable monomeric, oligomeric or macromolecular compound ofsynthetic, semisynthetic or biological origin, shows thermal, oxidativeand hydrolytic stability and resistance to delamination caused bymechanical stress and that said coating is permeable to gases, water,nutrients and ions having a molecular weight below 500 and has acontrolled permeability for bio-components, such as proteins,glycoproteins and lipids.

In a specifically preferred aspect of the present invention thesubstrate which is at least partially coated with a polymer as indicatedabove (secondary coating) is a biomedical material, article, or deviceincluding catheters and vascular grafts, especially an ophthalmic devicefor vision correction, such as a contact lens, an intraocular lens, oran extended wear contact lens and most specifically a lenticular cornealonlay or implant.

According to another embodiment of the present invention the degree ofcrosslinking of the primary polymer coating carrying reactive groups maybe further controlled by adding at least one crosslinking agent to themonomer feed which is subjected to after-glow plasma-inducedpolymerization.

According to a specific embodiment of the present invention a multilayerprimary coating having “tailored” permeability performance as well asdefined structure and morphology can be prepared by after-glowplasma-induced polymerization according to the present invention, if atfirst one or more polymerizable unsaturated compounds without reactivegroups, and then a polymerizable unsaturated compound carrying reactivegroups, each one optionally together with crosslinking agents and/orpolymerizable unsaturated compounds without reactive groups, aresubjected to polymerization one after the other, preferably withoutinterrupting the glow discharge.

A further subject matter of the present invention is a method forpreparing an article as indicated above which comprises carrying outafter-glow plasma-induced polymerization of a polymerizable unsaturatedcompound carrying reactive groups on a substrate wherein the substrateis positioned at a distance of 4 to 40 cm and the monomer inlet at adistance of 3 to 35 cm downstream outside the plasma zone.

Within the terms of the present invention, the plasma generation may begenerated by any means such as RF (radiofrequency), MW (microwave) or DC(direct current) technique. The sample temperature in the plasma reactoris typically in a range of 0-100° C., preferably in a range of 80-10°C., more preferably in a range of 80-50° C. and very preferably in arange of 40-20° C.

After-glow plasma induced polymerization of a polymerizable unsaturatedcompound carrying reactive groups in accordance with the invention istypically carried out under the following plasma conditions:

Electric power 40-300 watts, upper range up to 600 watts, applied poweris dependent upon reactive group (see examples) Electric voltage 8 · 10²− 4 · 10³ volts Plasma gas flow 1-100 (standard cubic centimeter) sccmMonomer flow 1-50 mg/min Feed gas flow 1-100 (sccm) Temp. of the monomersource −80° C. − +80° C. Frequency 1 kHz − 27.12 MHz, most preferably13.56 or 27.12 MHz Plasma gases Ar, He, N₂ Pressure 1 · 10⁻⁴ − 5 mbar,

Throughout the present invention, the term monomer or comonomer is usedequivalently to the expression, polymerizable unsaturated compound.

The substrate distance downstream from the plasma zone is preferably8-30 cm, most preferably 10-25 cm. The monomer inlet distance downstreamfrom the plasma zone is preferably 6-25 cm, most preferably 8-20 cm.Preferably an inductively-coupled, pulsed radio frequency glow dischargeplasma is used.

A further subject-matter of the present invention is an article having ahybrid-type coating obtainable by reaction of the article having apolymeric coating carrying reactive groups on the surface with asuitable monomeric, oligomeric or macromolecular compound of synthetic,semisynthetic or biological origin.

The polymeric coatings of the present invention carrying reactive groupswhich are obtainable by after-glow plasma-induced polymerization of apolymerizable unsaturated compound on a substrate under the conditionsmentioned regarding the distance between substrate and plasma zone aswell as monomer inlet and plasma zone are characterized—contrary tocoatings obtained by in-glow plasma-induced polymerization or byafter-glow plasma-induced polymerization without observing theseconditions—by the fact that the repeating units of the polymer chainsare to a large extent identical in structure to those repeating unitsobtained through a non-plasma radical polymerization of the respectiveunsaturated compound.

The uniform structure and the controllable relatively low degree ofcrosslinking of the coatings which is surprisingly achieved in theafter-glow or downstream embodiment of the plasma-induced polymerizationof a polymerizable unsaturated compound under the relatively mild plasmaconditions and the specific conditions of the position of substrate andmonomer inlet constitutes a characteristic feature of the coatings whichis responsible for a wide variety of advantageous properties exhibitedby these coatings, especially in view of their use in biological systemsincluding biomedical applications, articles or devices.

A specific advantage of the coatings is their strong adherence to thesurface of the coated substrate which is obtained to a large degreeindependently from the nature of the substrate, whether it is apolymeric organic material or an inorganic material such as a metal,metal oxide, ceramic material, glass or a mineral or carbon, especiallygraphite or glassy carbon. Also composite materials including two ormore of the above mentioned substrate materials may be coated with aprimary and/or secondary coating of the invention.

A further specific advantage of the primary polymeric coatings is thefact that they exhibit a high density of reactive groups on theirsurface providing a high number of linkage sites for the secondarycoating reaction with a suitable monomeric, oligomeric or macromolecularcompound of synthetic, semisynthetic or biological origin. The finalproduct, which results thereof, has a number of technically andbiologically advantageous properties including high wettability andbiocompatibility. This advantage follows from the unexpected findingthat the reactive groups of the polymerizable unsaturated monomer remainunaltered to a large extent during after-glow plasma-inducedpolymerization while they are decomposed almost entirely in in-glowplasma-induced polymerization and other plasma conditions describedabove, so that only very low surface functionality can be achieved.

The high degree of structural uniformity of the polymer chains, the lowdegree of crosslinking and the predominantly brush-type structure of thecoatings of the invention carrying reactive groups on the surface to thesubstrate provide the article having the final coating (primary coatingreacted with a monomeric, oligomeric or macromolecular compound ofsynthetic, semisynthetic or biological origin) of the invention withsuperior characteristics (according to the nature of the final coating)for a wide variety of applications including:

excellent adherence to the substrate and wear resistance;

excellent thermal, oxidative and hydrolytic stability and resistance todelamination caused by mechanical stress;

good permeation characteristics for liquids, gases, ions, nutrients andlow molecular weight compounds;

controlled permeability for biocomponents, such as proteins,glycoproteins and lipids;

high resistance against temperature changes, autoclaving, bioerosion,swelling and shear forces;

smooth surface down to the sub-micron area, uniform layer thickness andexcellent lubrication properties;

high resistance and durability in biological surroundings, goodresistance against formation of irreversible deposits of components frombiological systems, such as proteins, lipids, glycoproteins, salts andmetabolites and cell debris;

low tendency for absorption of substances from the surroundings, such ascosmetics, solvent vapors and dusts;

no tendency for adherence of microorganisms.

The extraordinary features of the primary as well of the final,hybrid-type coating with regard to biocompatibility, bioaffinity,bioactivity and in general to resistance against formation ofirreversible deposits as well as to permeability are due to the factthat polymer chains within the coating still possess pronounced dynamicsand mobility. In biological surroundings, secondary (or hybrid-type)coatings show in general a substantially reduced tendency to causedenaturation of biocomponents. Moreover, through proper choice of theconstituents of the final coating the bioadhesion properties of abiomechanical device or of a membrane can be varied within wide ranges.The coatings can thus provide a substrate with such contradictoryeffects as improved cell attachement and tissue integration forartificial organ applications and anti-biofouling for membrane systems.

As mentioned above, there is substantially no limitation with respect tothe form of the substrate to be coated for preparation of an articleaccording to the invention, as long as it can be brought into and heldin the after-glow zone of a plasma generating device. Specific examplesof forms of substrates which may be coated according to the inventioninclude films, fibers, membranes, sheets, hoses, tubes, hollow fibers,capsules, beads and granules of different size including powder typematerials as well as composites and laminates. A specific group ofsubstrates which is envisaged within this invention are biomedicalmaterials or articles, especially ophthalmic devices for visioncorrection. These include lenticular corneal implants (artificialcornea), contact lenses and intraocular lenses.

The substrate includes e.g. any material conventionally used for themanufacture of biomedical devices, e.g. contact lenses, which are notsufficiently hydrophilic and/or biocompatible per se. Such materials areknown to the person skilled in the art and may comprise for examplepolysiloxanes, fluorinated (meth)acrylates or equivalent fluorinatedcomonomers derived e.g. from other polymerizable carboxylic acids, alkyl(meth)acrylates or equivalent alkyl comonomers derived from otherpolymerizable carboxylic acids, or fluorinated polyolefins, such asfluorinated ethylene or propylene polymers and copolymers, ortetrafluoroethylene, preferably in combination with specific dioxols,such as perfluoro-2,2-dimethyl-1,3-dioxol.

The substrate also includes any material conventionally used for themanufacture of biomedical devices, e.g. contact lenses, which arehydrophilic per se, since functional groups, e.g. amine or hydroxygroups are inherently present in the material and therefore also at thesurface of a biomedical device manufactured therefrom. In this case aspecific interphase layer between the substrate and the primary coatingcan be formed through reaction of the functional groups of the substrateand the coating. Such materials are known to the person skilled in theart. Typical examples comprise e.g. Polymacon, Tefilcon, Methafilcon,Deltafilcon, Bufilcon, Phemfilcon, Ocufilcon, Focofilcon, Etafilcon,Hefilcon, Vifilcon, Tetrafilcon, Perfilcon, Droxifilcon, Dimefilcon,Isofilcon, Mafilcon or Atlafilcon. Most of these materials are HEMA andor NVP based, but suitable materials may also be based on otherunderlying monomers or polymers having reactive groups, e.g. hydroxygroups or amino groups, such as e.g. polyvinyl alcohol.

A polymer substrate, in particular a polymer which is suitable as anartificial cornea, e.g. a corneal onlay, might be coated, preferably onits its outer (front) surface, with a hybrid-type coating according tothe present invention. Such a hybrid-type coating promotes typically aselective growth of tissue (e.g. corneal epithelial cells) on said outersurface. Typical secondary coating materials of such hybrid-typecoatings are peptides, proteins, glycoproteins, carbohydrates,polysacharides such as collagen, laminin, albumin, extracellular matrixproteins, cell adhesion proteins, growth factors, fibronectin,vitronectin, chondronectin, fibrin, globulins, muscle fibre proteins,vitrogen, genetically engineered peptides and proteins, lectins,hirudin, mucin, chondroitin sulfate, aminodextran, hyaluronic acid,sialic acid, L-fucose, N-acetyl galactosamin and/or derivatives, activefragments and mixtures thereof. Fibronectin, collagen, epidermal growthfactors and/or derivatives, active fragments and mixtures thereof areparticularly useful. A surface coating of this type can typicallyexhibit a plurality of advantageous properties, for example theattachment of cells with good biostability and resistance to deposits.

The inner (back) surface of an artificial cornea, e.g. a corneal onlaylenticule might be coated with another coating (relative to the frontsurface), e.g. as follows:

(a) Either with a primary coating carrying reactive groups according tothe present invention, such as OCN— or epoxy groups, for the firmbinding of the onlay to the underlying material of the corneal BasementMembrane or Bowman's Membrane through chemical reaction, or;

(b) With a secondary hybrid-type coating according to the presentinvention, which mediates strong affinity of the onlay to the underlyingmaterial of the Basement Membrane or Bowman's Membrane and in a specificembodiment of the invention prevents corneal epithelial cell attachmentand growth on this back surface.

In case of an artificial cornea device designed for implantation intothe corneal stroma (corneal inlay) both surfaces can be coated accordingto the present invention with a hybrid-type coating, which provides goodlong-term biocompatibility and tissue integration to the implant.

The polymer substrate may be any blood-contacting materialconventionally used for the manufacture of renal dialysis membranes,blood storage bags, pacemaker leads or vascular grafts. For example, thesubstrate may be a polyurethane, polydimethylsiloxane,polytetrafluoroethylene, perfluoro-alkyl-polyether, polyvinylchloride orDacron™.

In a specifically preferred embodiment of the present invention thesubstrate to be coated (with a secondary coating) is a contact lenssuitable for extended wear, i.e. for continuous wear of more than sixdays and six nights up to a time of about 30 days. This type of softcontact lenses includes those comprising polysiloxane and/orperfluoroalkyl-polyether groups which exhibit the desired high oxygen-as well as high ion- and water-permeability. If this type of substrateis coated in accordance with the present invention with a hydrophiliccompound, coated contact lenses are obtained which exhibit the followingdesirable properties as compared to conventionally surface coatedcontact lenses:

increased permeability for oxygen, carbon dioxide, water and ions;

excellent wettability, lubricity and stability in the ocular liquidsurroundings;

improved comfort for the wearer as well as resistance againstirreversible deposition on the surface of the lens of substancesoccurring in the ocular surroundings, including proteins, lipids, mucinsand salts;

decreased adhesiveness for microorganisms;

decreased tendency of microcrack formation within the coating duringsterilization in the autoclave in phosphate buffered saline;

superior on-eye performance including very low cornea swelling, eyeirritation and very good lens mobility on the eye during continuous wearof the lens over an extended time of up to 30 days.

In the case of implants a secondary coating in accordance with thepresent invention prepared from a suitable biomaterial or a hydrophilicsynthetic compound provides articles having surface and permeabilitycharacteristics including an open, only slightly cross-linked polymerstructure which exhibits excellent biocompatibility and leads to firmcell adhesion and to good and durable integration into the livingtissue.

The monomer which may be used to prepare the primary coating carryingreactive groups by after-glow plasma-induced polymerization may be anypolymerizable unsaturated compound which carries reactive groups and canbe evaporated and introduced into the after-glow zone of a plasmagenerating apparatus to contact the substrate provided therein.

Examples of reactive groups to be contemplated herein include isocyanate(—NCO), isothiocyanate (—NCS), epoxy, anhydride, azlactone and lactone(e.g. β-, γ-,δ-lactone) groups.

An azlactone is particularyl preferred, since it exhibits a higherselectivity, in particular when the primary reactive plasma coating isreacted with amino-group containing compounds, e.g. with proteins inaqueous solutions. The stability in such aqueous solutions at roomtemperature is higher too.

Specific examples of preferred polymerizable unsaturated compoundscarrying reactive groups are 2-isocyanatoethyl-methacrylate (IEM),glycidyl methacrylate, (meth)acrylic acid anhydride and4-vinyl-2,2-dimethylazlactone.

The article having a primary polymeric coating carrying reactive groupswhich constitutes one subject-matter of the invention is a kind ofintermediate product which is reacted with a monomeric, oligomeric ormacromolecular compound of synthetic, semisynthetic or biological originproviding desirable surface properties including wettability to thefinal laminate coated product. Specific examples of a monomeric,oligomeric or macromolecular compound of synthetic, semisynthetic orbiological origin envisaged as top coatings which may be used formodifying the reactive surface are proteins, such as albumin, hirudinand lectins; glycoproteins, such as mucin; carbohydrates, such ascyclodextrines or 8-aminooctyl-lactobionoamide; polysaccharides, such aschitosan; and amino functionalized polymers and telomers such asJeffamines and polyvinylalcohol (PVA), poly-N-vinyl pyrrolidone(poly-NVP), polyethylene glycol (PEG) and poly-acrylamide.

The primary polymeric coatings carrying reactive groups are prepared onat least a part of the surface of a substrate to give a coated articlehaving a reactive surface by plasma-induced polymerization of apolymerizable unsaturated compound in the after-glow or downstream areaof a plasma reactor. The process parameter including the physical plasmaparameters of the deposition process are controlled in such a way thatthe desired amount of repeating units which are identical in structureto those repeating units obtained by non-plasma radical polymerizationof the polymerizable unsaturated compound, the desired degree ofcrosslinking and the desired morphology and topography are obtained onthe specific substrate. These parameters and characteristics as well asthe thickness of the coating may be tailored within broad ranges bysuitably selecting the plasma and reaction parameters. Compared to othercoating processes the method of preparing polymeric coatings carryingreactive groups according to the invention offers the followingadvantages (e.g. for coating contact lenses):

the coated substrates are obtained under sterile conditions;

very low surface erosion and high deposition rate;

smooth, pinhole-free coatings are obtained;

the thickness of the coating can easily be controlled up to relativelythick coatings of more than 1 μm;

low content of radicals remaining in the coating;

no uncontrolled secondary reactions with air to hydroperoxides and otherreactive species;

excellent thermal and hydrolytic stability of the coatings which do notcontain leachable parts;

high UV and light stability of the coatings;

uniform layer thickness on non-flat substrates including good edgecoating;

homogenous surface groups;

high content of “brush-type” surface structures with low tendency fordenaturation of biopolymers or other biocomponents and irreversibleadsorption (biofouling);

no fragmentation of the monomers employed and no bombardment of thesurface of the substrate by atoms, ions, excited species or high energyUV-radiation during the coating process leading to undesired secondarychanges of the coating and/or the substrate and to detrimental surfaceerosion.

no tendency to delamination of the coatings on thermal, hydrothermal andmechanical stress.

The articles of the present invention having a hybrid-type(secondary)coating obtainable by reaction of the reactive groups presenton the (primary) coating obtained by after glow plasma-inducedpolymerization with a suitable monomeric, oligomeric or macromolecularcompound of synthetic, semisynthetic or biological origin exhibitbioactive, biocompatible and wettable coatings on a wide variety ofbiomaterials including artificial cornea and contact lenses and impartspecific (bio)affinity or (bio)activity properties to such a device. Asmentioned before, catalysts, enzymes, antibodies and similar materialsmay also be immobilized by reaction with the reactive groups present onthe said primary polymeric coating.

As mentioned before, the reactive groups of the primary coating may bemodified with substantially any suitable molecule or compound which iscapable of forming an addition reaction with a corresponding reactivegroup. Examples of suitable molecules or compounds range from smallmolecules such as ammonia, water, alcohol to highly complex compoundssuch as enzymes, glycoproteins or nucleotides. Further specific examplesare listed above.

The reactive groups may be modified by these compounds in solution or inpure form. If pure and if appropriate, they may be applied as a gas or aliquid. Solvents suitable for solutions should be substantially inert tothe reactive groups or should at least exhibit a clearly attenuatedreactivity in comparison to the reactivity of the compound to be added.Suitable examples thereof are ethers, such as tetrahydrofuran (THF),diethyl ether, diethylene glycol dimethyl ether or dioxane, halogenatedhydrocarbons, such as chloroform or methylene chloride, bipolar aproticsolvents, such as acetonitrile, acetone, dimethylformamide (DMF) ordimethyl sulfoxide (DMSO), hydrocarbons, such as hexane, petroleumether, toluene or xylene, and furthermore pyridine orN-methylmorpholine.

The temperatures used in an above secondary modification reaction rangetypically from −20° C. to 150° C., preferably from 0-100° C. and inparticular from 20-60° C. The reaction time ranges typically from a fewseconds to several days, preferably from about 30 seconds to 24 hoursand more preferably from 1 minute to 12 hours.

The reaction of a reactive group with a molecule or a compound may bemonitored with several analytical methods such as spectroscopy. Specificmethods thereof are Fourier Transformation Infrared—Attenuated TotalReflection Spectroscopy (FTIR-ATR), ESCA, Electron Spin Resonace (ESR)and TOF-SIMS.

An above molecule or compound may either be used separately or inmixtures. It is not a prerequisite that in such a mixture the compoundsor molecules present exhibit comparable reactivities. To the contrary,such might be used for limiting the quantity of a certain species on acoating surface. If appropriate, said final coating may be carried outin several steps sequentially. Another method for limiting the amount ofa species on a final coating is for example the addition of a highlyreactive gas, which would immediately quench the addition reaction whenneeded.

A third possibility for graded surface loading exists in using mixturesof polymerizable unsaturated compounds carrying reactive groups andpolymerizable unsaturated compounds carrying no reactive groups for theprimary plasma-induced polymerization thus generating primary surfacesof graded functionality. Typically, the relative amount of polymerizableunsaturated compounds carrying reactive groups ranges in wt. % from100%-10%, preferably from 80%-50%, and more preferably from 70%-40%; theremainder to 100 wt. % being a polymerizable unsaturated compoundcarrying no reactive group.

The thickness of a final polymeric hydrid-type coating is typically inthe range of 1 to 5′000 nm, preferably in the range of 5 to 1′000 and inparticular from 10 to 500 nm.

As already mentioned above, in an important aspect, the presentinvention refers to contact lenses comprising a final coating accordingto the invention on a suitable lens body which—because of theoutstanding properties of the coating including high oxygentransmissibility, high permeability for ions and water and good movementon the eye—may be used for extended periods of wear, e.g., up to 30days. Important characteristics of such contact lenses and methods fortheir determination will be explained infra. Many of these aspects areimportant for artificial cornea as well. In addition, artificial corneaapplications require protein permeability.

Oxygen Transmibility and Permeability

The “oxygen transmissibility of a lens, as used herein, is the rate atwhich oxygen will pass through a specific ophthalmic lens. Oxygentransmissibility, D_(k)/t, is conventionally expressed in units ofbarrers/mm, where t is the average thickness of the material [in unitsof mm] over the area being measured and “barrer” is defined as:

[(cm³ oxygen) (mm)/(cm²) (sec) (mm Hg)]·10⁻⁹

The “oxygen permeability”, D_(k), of a lens material does not depend onlens thickness. Oxygen permeability is the rate at which oxygen willpass through a material. Oxygen permeability is conventionally expressedin units of barrers, where “barrer” is defined as:

[(cm³ oxygen) (mm)/(cm²) (sec) (mm Hg)]·10⁻¹⁰

These are the units commonly used in the art. Thus, in order to beconsistent with the use in the art, the unit “barrer” will have themeanings as defined above. For example, a lens having a D_(k) Of 90barrers (“oxygen permeability barrer”) and a thickness of 90 microns(0.090 mm) would have a Dk/t of 100 barrers/mm (“oxygen transmissibilitybarrers”/mm).

The oxygen transmissibility of the extended-wear lens from the outersurface to the inner surface must be sufficient to prevent anysubstantial corneal swelling during the period of extended wear. It isknown that the cornea swells approximately 3% to 4% during overnightperiods of sleep when the eyelids are closed, as a result of oxygendeprivation. It is also known that wearing a conventional contact lensfor a period of about 8 hours (overnight wear) causes corneal swellingof about 11%. However, an acceptable extended-wear contact lens willproduce, after wear of about 24 hours, including normal sleep periods,corneal swelling of less than about 8%, more preferably less than about6%, and most preferably less than about 4%. A preferred extended-wearcontact lens will produce, after wear of about 7 days, including normalsleep periods, corneal swelling of less than about 10%, more preferably,less than about 7%, and most preferably less than about 5%. Thus, theextended wear lens must have oxyperm polymer in an amount sufficient toproduce oxygen diffusion to yield the above properties relating tocorneal swelling. Preferably, the extended-wear lens has a continuousphase of oxyperm polymer extending from the outer surface to the innersurface of the lens.

The oxygen permeability of a lens and oxygen transmissibility of a lensmaterial may be determined by the following technique. Oxygen fluxes (J)are measured at 34° C. in a wet cell (i.e., gas streams are maintainedat about 100% relative humidity) using a Dk1000 t:-4 instrument(available from Applied Design and Development Co., Norcross, Ga.), orsimilar analytical instrument. An air stream, having a known percentageof oxygen (e.g., 21%), is passed across one side of the lens at a rateof about 10 to 20 cm³/min., while a nitrogen stream is passed on theopposite side of the lens at a rate of about 10 to 20 cm³/min. Thebarometric pressure surrounding the system, P_(measured), is measured.The thickness (t) of the lens in the area being exposed for testing isdetermined by measuring about 10 location with a Mitotoya micrometerVL-50, or similar instrument, and averaging the measurements. The oxygenconcentration in the nitrogen stream (i.e., oxygen which diffusesthrough the lens) is measured using the DK1000 instrument. The oxygenpermeability of the lens material, D_(k), is determined from thefollowing formula:

D _(k) =Jt(P _(oxygen))

where

J=oxygen flux [microliters_(O2)/cm²-minute]

P_(oxygen)

=(P_(measured)−P_(water vapor))·(% O₂ in air stream) [mm Hg]

=partial pressure of oxygen in the air stream

P_(measured)=barometric pressure [mm Hg]

P_(water vapor)=0 mm Hg at 34° C. (in a dry cell) [mm Hg]

P_(water vapor)=40 mm Hg at 34° C. (in a wet cell) [mm Hg]

t=average thickness of the lens over the exposed test area [mm]

where D_(k) is expressed in units of barrers, i.e., [(cc oxygen)(mm)/cm²]·[sec/mm Hg]·10⁻¹⁰.

The oxygen transmissibility (D_(k)/t) of the material may be calculatedby dividing the oxygen permeability (D_(k)) by the average thickness (t)of the lens.

The oxygen transmissibility (D_(k)/t) of the extended-wear lens of theinvention is preferably at least 70 barrers/mm, more preferably at least75 barrers/mm, and most preferably at least 87 barrers/mm. The lenscenter thickness is typically more than about 30 microns, preferablyabout 30 to about 200 microns, more preferably about 40 to about 150microns, even more preferably about 50 to about 120 microns, and mostpreferably about 60 to 100 microns.

Ionoflux Measurement Technique

The following technique, referred to herein as the “Ionoflux Technique”,is a preferred method for determining the ion permeability of a lens.This technique may be used to determine the likelihood of adequateon-eye movement.

The “Ionoflux Technique” involves the use of a conductometer (LF 2000/C,catalog, no. 300105, Wissenschaftlich-Technische Werkstätten GmbH (WTW),Germany), an electrode equipped with a temperature sensor (LR 01/T,catalog no. 302 520, (WTW)), a donor chamber containing a salt solution,a receiving chamber containing about 60 ml of deionized water, a stirbar and a thermostat.

The donor chamber is specially designed for sealing a contact lensthereto, so that the donor solution does not pass around the lens (i.e.,ions may only pass through the lens). The donor chamber is composed of aglass tube which is threaded at the end which is immersed in thereceiving solution. The glass tube includes a centrally located hole ofabout 9 mm in diameter. A lid, which is threaded to mate with the glasstube, holds a lens-retaining member which includes a centrally locatedhole of about 8 mm in diameter. The lens-retaining member includes amale portion adapted to mate with and seal the edges of the inner(concave) surface of a lens and a female portion adapted to mate withand seal the edges of the outer (convex) surface of a lens.

The lens to be measured is placed in the lens-retaining device, betweenthe male and female portions. The male and female portions includeflexible sealing rings which are positioned between the lens and therespective male or female portion. After positioning the lens in thelensretaining device, the lens-retaining device is placed in thethreaded lid. The lid is screwed onto the glass tube to define the donorchamber. The donor chamber is filled with 16 ml of 0.1 molar NaClsolution. The receiving chamber is filled with 60 ml of deionized water.The leads of the conductivity meter are immersed in the deionized waterof the receiving chamber and a stir bar is added to the receivingchamber. The receiving chamber is placed in a thermostat and thetemperature is held at about 35° C. Finally, the donor chamber isimmersed in the receiving chamber.

Measurements of conductivity are taken every 20 minutes for about threehours, starting 10 minutes after immersion of the donor chamber into thereceiving chamber. The Ionoflux Diffusion Coefficient, D, is determinedby applying Fick's law as follows:

D=−n′/(A·dc/dx)

where

n′=rate of ion transport [mol/min]

A=area of lens exposed [mm²]

D=Ionoflux Diffusion Coefficient [mm²/min]

dc=concentration difference [mol/L]

dx=thickness of lens [mm]

An Ionoflux Diffusion Coefficient of greater than about 6.4·10⁻⁶ mm²/minis preferred for achieving sufficient on-eye movement. More preferably,the Ionoflux Diffusion Coefficient is greater than about 2.6·10⁻⁶mm²/min, while most preferably the Ionoflux Diffusion Coefficient isgreater than about 1.5·10⁻⁵ mm²/min. It must be emphasized that theIonoflux Diffusion Coefficient correlates with ion permeability throughthe lens, and thereby is a predictor of on-eye movement.

Contact Angle Measurements

Advancing and receding water contact angles of coated and non-coatedlenses were determined with the dynamic Wilhelmy method using a KrüssK12 instrument (Krüss GmbH, Hamburg). For details it is referred to D.A. Brandreth: “Dynamic contact angles and contact angle hysteresis”,Journal of Colloid and Interface Science, vol. 62, 1977, pp. 205-212 andR. Knapikowski, M. Kudra: Kontaktwinkelmessungen nach demWilhelmy-Prinzip-Ein statistischer Ansatz zur Fehierbeurteilung”, Chem.Technik, vol. 45, 1993, pp. 179-185.

Concentration of Functional Groups Generated on a Substrate Surface byAfter-glow Plasma Induced Polymerization of Unsaturated ReactiveMonomers

(1) Through reaction of the functional groups within the primary plasmacoating with a solution of the spin label4-amino-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-amino-TEMPO) aquantitative conversion can be achieved. Subsequent Electron SpinResonance (ESR) spectroscopy of the samples thus labeled leads to ahighly sensitive and reliable determination of the primary functionalgroups. Dependant on the type of the reactive monomer and on thepercentage of additional non-reactive (or unreactive) comonomers usedsurface functionalities ranging from 0.2-20·10⁻⁹ Mol/cm² , preferablyfrom 0.5-15·10⁻⁹ Mol/cm² and in particularly from 2-12·10⁻⁹ Mol/cm² canbe made.

(2) The functional surface groups can clearly be identified by FourierTransform Infrared Attenuated Total Reflection (FTIR-ATR) Spectroscopy.The absorption bands employed for the quantification may typically be:

isocyanate: 2270 cm⁻¹, epoxide: 1270 cm⁻¹ anhydride: 1800, 1760 cm⁻¹,azlactone: 1820, 1770 cm⁻¹

FTIR-ATR can advantageously be used for the follow up on the consumptionof functional groups during the secondary reaction with monomers,oligomers, polymers or biomaterials.Dependant on the reactivity, themolecular weight and the total functionality of the molecular speciesused, 60-95% conversion of the primary functional surface groups can beachieved. Typically, the residual surface functionality mightsubsequently be completely quenched by reaction with reactive smallmolecules like NH₃.

(3) An indirect determination of the total surface loading in monomers,oligomers, polymers or of any biomaterial obtained by secondary reactioncan be accomplished by reacting the residual functionality with4-amino-TEMPO and subsequent ESR spectroscopy. The difference betweenthe original ESR functionality and the residual ESR functionality leadsto a conclusion on the total surface loading achieved with the provisionthat no side reactions with solvent molecules or moisture or the likeoccur. The results derived from the calculation are within standarddeviations (±10%) in satisfactory agreement with the conclusions drawnfrom FTIR-ATR measurements. Conversions of functional groups in thesecondary reactions range from 60-98%.

Polymerizable unsaturated compounds carrying no reactive groups aretypically hydrophobic or hydrophilic vinylic comonomers or mixturesthereof.

Suitable hydrophobic vinylic comonomers include, without this being acomprehensive list, C₁-C₁₈alkyl acrylates and methacrylates,C₃-C₁₈alkylacrylamides and -methacrylamides, acrylonitrile,methacrylonitrile, vinyl C₁-C₁₈alkanoates, C₂-C₁₈ alkenes, C₂-C₁₈haloalkenes, styrene, C₁-C₆ alkylstyrene, vinyl alkyl ethers in whichthe alkyl moiety has 1 to 6 carbon atoms, C₂-C₁₀perfluoroalkyl acrylatesand methacrylates and correspondingly partially fluorinated acrylatesand methacrylates, C₃-C₁₂perfluoroalkyl ethylthiocarbonylaminoethylacrylates and -methacrylates, acryloxy- and methacryloxyalkylsiloxanes,N-vinylcarbazole, C₁-C₁₂alkyl esters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given to, forexample, C₁-C₄alkyl esters of vinylically unsaturated carboxylic acidshaving 3 to 5 carbon atoms or vinyl esters of carboxylic acids having upto 5 carbon atoms.

Examples of suitable hydrophobic vinylic comonomers include methylacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethylmethacrylate, propyl methacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyltoluene, vinyl ethyl ether,perfluorohexylethylthiocarbonylaminoethyl methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoroisopropylmethacrylate, hexafluorobutyl methacrylate,tris(trimethylsilyloxy)silylpropyl methacrylate,3-methacryloxypropylpentamethyldisiloxane andbis(methacryloxypropyl)tetramethyldisiloxane.

Suitable hydrophilic vinylic comonomers include, without this being acomprehensive list, hydroxy-substituted lower alkyl acrylates andmethacrylates, acrylamide, methacrylamide, lower alkylacrylamides and-methacrylamides, methoxylated acrylates and methacrylates,hydroxy-substituted lower alkyl-acrylamides and -methacrylamides,hydroxy-substituted lower alkyl vinyl ethers, sodium ethylenesulfonate,sodium styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid,N-vinylpyrrole, N-vinylsuccinimide, N-vinylpyrrolidone, 2- and4-vinylpyridine, acrylic acid, methacrylic acid, amino- (where the term“amino” also covers quaternary ammonium), mono(lower alkyl)amino- ordi(lower alkyl)-amino(lower alkyl) acrylates and methacrylates allylalcohol and the like. Preference is given to, for example,hydroxy-substituted C₂-C₄alkyl (meth)acrylates, five- to seven-memberedN-vinyllactams, N,N-di-C₁-C₄alkyl(meth)acrylamides and vinylicallyunsaturated carboxylic acids having a total of 3 to 5 carbon atoms.

Examples of suitable hydrophilic vinylic comonomers include hydroxyethylmethacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide,dimethylacrylamide, allyl alcohol, vinylpyridine, vinylpyrrolidone,glycerol methacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide and thelike.

Preferred hydrophobic vinylic comonomers are methyl methacrylate andvinyl acetate.

Preferred hydrophilic vinylic comonomers are 2-hydroxyethylmethacrylate, N-vinylpyrrolidone and acrylamide.

Examples of typical polyunsaturated or cross-linking comonomers orcross-linking agents are allyl (meth)acrylate, lower alkylene glycoldi(meth)acrylate, poly(lower alkylene) glycol di(meth)acrylate, loweralkylene di(meth)acrylate, divinyl ether, divinyl sulfone, di- andtrivinylbenzene, trimethylolpropane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, bisphenol A di(meth)acrylate,methylenebis(meth)acrylamide, triallyl phthalate and diallyl phthalate.

The present invention is further explained with reference to specificembodiments in the following examples. All temperatures are given inDegrees Centigrade.

EXAMPLE A-1

(Preparation of amino-terminated poly-N-vinyl-2-pyrrolidone)

Distilled N-vinyl-2-pyrrolidone (NVP) 55.58 g (0.50 Mol),2-aminoethanethiol (Cysteamine) 2.33 g (30 mmol), andazo-bisisobutyronitrile (AIBN) 0.74 g (4.5 mmol) are mixed with 100 mlof absolute ethanol in a 350 ml three-neck flask, equipped with amechanical stirrer, a reflux condenser and thermometer. The flask isthen evacuated to a pressure of 600 mbar and a slow stream of nitrogenis used to deoxygenate the solution. This step is repeated 10 times. Thesolution is then heated to 60° C. After 28 hours of stirring at 60° C.under a nitrogen atmosphere, the solution is cooled to room temperatureand stirred under nitrogen for a further 12 hours. The amino-terminatedpolymer is precipitated from 2 liter of anhydrous ethyl ether. The solidis dissolved in 200 ml of THF, and this reprecipitation is repeatedtwice. The white solid, 12.32 g (23% yield) is dried under reducedpressure for 48 hours and analyzed. The M_(W) of the polymer is about71,000, amino titration of the telomeric product is found to be 0.014mVal/g.

EXAMPLE A-2

Preparation of a polyvinyl alcohol with pendant amino groups. PVA ofM_(W)˜18,000, carrying approximately 9 amino groups per chain wasprepared in accordance with the first reaction step of Example 6 inEP-A-641 806. Consequently a 10% PVA-solution (Moviol 4-88, Hoechst) aremixed with 2.4 g (14.8 mmol) aminobutyraldehyde-diethylacetal (Fluka)and 20 g hydrochloric acid (37%). This mixture is stirred for 48 hoursat room temperature. Subsequently said solution is neutralized with anaqueous (10% wt.) sodium hydroxide solution. This solution contains thetitle compound.

EXAMPLE A-3

(Macromer Synthesis)

51.5 g (50 mmol) of the perfluoropolyether Fomblin, ZDOL (from AusimontS.p.A., Milan) having a mean molecular weight of 1030 g/mol andcontaining 1.96 meq/g of terminal hydroxyl groups according to end-grouptitration is introduced into a three-neck flask together with 50 mg ofdibutyltin dilaurate. The flask contents are evacuated to about 20 mbarwith stirring and subsequently filled with argon. This operation isrepeated twice. 22.2 g (0.1 mol) of freshly distilled isophoronediisocyanate kept under argon are subsequently added in a counterstreamof argon. The temperature in the flask is kept below 30° C. by coolingwith a waterbath. After stirring at overnight room temperature, thereaction is complete. Isocyanate titration gives an NCO content of 1.40meq/g (theory: 1.35 meq/g).

202 g of the α,ω-hydroxypropyl-terminated polydimethyl-siloxane KF-6001from Shin-Etsu having a mean molecular weight of 2′000 g/mol (1.00 meq/gof hydroxyl groups according to titration) are introduced into a flask.The flask contents are evacuated to approx. 0.1 mbar and filled withargon. This operation is repeated twice. The degassed siloxane isdissolved in 202 ml of freshly distilled toluene kept under argon, and100 mg of dibutyltin dilaurate (DBTDL) are added. After completehomogenization of the solution, all the perfluoropolyether reacted withisophorone diisocyanate (IPDI) is added under argon. After stirringovernight at room temperature, the reaction is complete. The solvent isevaporated under a high vacuum at room temperature. Microtitration shows0.36 meq/g of hydroxyl groups (theory 0.37 meq/g). 13.78 g (88.9 mmol)of 2-isocyanatoethyl methacrylate (IEM) are added under argon to 247 gof the α,ω-hydroxypropyl-terminatedpolysiloxane-perfluoropolyether-polysiloxane three-block copolymer (atriblock copolymer on stoichiometric average, but other block lengthsare also present). The mixture is stirred at room temperature for threedays. Microtitration then no longer shows any isocyanate groups(detection limit 0.01 meq/g). 0.34 meq/g of methacryloyl groups arefound (theory: 0.34 meq/g).

The macromer prepared in this way is completely colorless and clear. Itcan be stored in air at room temperature for several months in theabsence of light without any change in molecular weight.

EXAMPLE A-4

(Preparation of a Contact Lens)

13.0 g of the macromer from Example A-3 are dissolved in 5.6 g ofethanol (Fluka, puriss. p.a.) (70% by weight solution). After completehomogenization of the solution, 5.2 g of3-tris(trimethylsiloxy)silylpropyl methacrylate (TRIS from Shin-Etsu,product No. KF-2801), 7.8 g of freshly distilled N,N-dimethylacrylamide(DMA) and 160 mg of the photoinitiator Darocur®1173 (Ciba) are added.This solution is filtered through a Teflon membrane having a pore widthof 0.45 μm under an argon pressure ranging from 1 to 2 atm. The filteredsolution is frozen in a flask in liquid nitrogen, the flask is evacuatedunder a high vacuum, and the solution is returned to room temperaturewith the flask sealed. This degassing operation is repeated twice. Theflask containing the macromer/comonomer solution is then transferredinto a glove box with an inert-gas atmosphere, where the solution ispipetted into dust-free contact-lens molds made from polypropylene. Themolds are closed, and the polymerization reaction is effected by UVirradiation (15 mW/cm², 5 min.), with simultaneous crosslinking. Themolds are then opened and placed in ethanol, causing the resultantlenses to swell out of their molds. The lenses are extracted for 24hours with constantly replenished distilled dichloromethane andsubsequently dried in a high vacuum. The dried lenses are equilibratedin phosphate-buffered physiological saline solution inautoclave-resistant vials and then autoclaved at 120° C. for 30 minutes.All physical data measurements are carried out on autoclaved lenses.

The lenses produced in this way are characterized by the followingvalues: oxygen permeability (Dk) 77 barrer (determined by the “wet”method described above), water content of the equilibrated lenses 32% byweight, elongation at break at 35° C. 360% modulus of elasticity 30° C.0.5 MPa (measured using a Minimat from Polymer Laboratories, UK).

EXAMPLE A-5

(Preparation of 8-aminooctyl Iactobionic Acid Amide)

A suspension of 40 g (0.12 Mol) of lactobionolactone (Solvay, Germany)in 400 ml of methanol is added to a solution of 22 g (0.15 Mol) of1,8-diaminooctane in 200 ml of methanol stirring in a three-neck flaskequipped with a thermometer, a mechanical stirrer and a refluxcondenser. After 24 hours of reflux under a nitrogen atmosphere, 5 g ofactivated charcoal is added to the flask and after 5 minutes of stirringthe solution is filtered through a 1 cm thick layer of silica gel andhyflo. The slightly yellow solution is then concentrated uponevaporation to a volume of about 100 ml and after cooling to about 5°C., 20 ml of acetonitrile and 20 ml of diethyl ether are added toinitiate crystallization. After 3 days of standing at 5° C., thecrystalline product is filtered off and dried under a reduced pressurefor 12 hours.

% C % H % N Calculated 49.58 8.32 5.78 Found 49.68 7.99 5.56

Titration of amino groups: 1.80 mVal/g (titration with 0.1 N HClO₄).

EXAMPLE A-6

5-aminopentyl-β-cyclodextrin is prepared in accordance with theprocedure described in example 16 of patent application WO 95/03336 (S.Hanessian).

EXAMPLE A-7

(Macromer Synthesis)

Reaction of β,ω-bis-3-aminopropyl-dimethylpolysiloxane with D(+)gluconicacid δ-lactone:

Before the reaction, the amino-functionalized poly-dimethylsiloxaneemployed for the synthesis (X-22-161-C, Shin Estu, JP) was finelydispersed in acetonitrile, extracted and then subjected to distillationin a thin layer evaporator at 10⁻⁴ Torr.

The following reactions take place with exclusion of H₂O. 200 g ofpurified amino-functionalized polydimethyl-siloxane (0.375 meq of NH₂/g;Mn(VPO) 3,400-3,900 (VPO, Vapor Pressure Osmometry)), dissolved in 200ml of absolute THF, are slowly added dropwise to a suspension of 13.35 g(75 mmol) of D(+) gluconic acid δ-lactone in 50 ml of absolute THF, andthe mixture is stirred at 40° C. for about 24 hours until the lactonehas reacted completely. (Monitoring of the reaction by thin layerchromatography (TLC): silica gel; i-propanol/H₂O/ethyl acetate 6:3:1;staining with Ce(IV) sulfate/phosphoromolybdic acid solution (CPSreagent)). The reaction mixture is then concentrated to dryness and theresidue is dried at 0.03 mbar for 48 hours. 213.3 g ofβ,ω-bis(3-gluconamidopropyl)-poly-dimethylsiloxane are obtained.Titration of the amino groups with perchloric acid shows a conversion ofthe amino groups of 99.8%.

Reaction of β,ω-bis-(3-gluconamidopropyl)-dimethylpolysiloxane with IEM

The product obtained above (213.3 g) is dissolved in 800 ml of absoluteTHF and the solution is heated to 40° C. followed by the addition ofcatalytic amounts of dibutyltin dilaurate (DBTDL). 14 g (90 mmol) of IEMdissolved in 20 ml of absolute THF are added dropwise to this solutionover a period of about 4 hours. This corresponds to a concentration of1.2 equivalents of IEM per gluconamide unit. The reaction is carried outin the course of 48 hours (monitoring of the reaction by IR spectroscopydetection of the NCO bands). The reaction mixture is concentrated andthe product is dried in a brown glass flask under 3 Pa (0.03 mbar) for24 hours, while cooling with ice. 227.2 g of a colorless rubbery andelastic product of high optical transparency are obtained.

EXAMPLE A-8

(Preparation of a Contact Lens)

Before polymerization, the acrylic monomers employed,N,N-dimethylacrylamide (DMA) and3-methacryloyloxypropyl-tris(trimethylsilyloxy)silane (TRIS) are eachpurified from inhibitors by distillation. 0.80 g (8.1 mmol) of DMA and0.804 g (1.9 mmol) of TRIS are placed in a 50 ml round-bottomed flask,and the flask is flushed with N₂ for half an hour, while cooling withice. 0.80 g of the macromer prepared according to Example A-7 aretransferred to a round-bottomed flask with a nitrogen gas inlet,degassed under 3 Pa (0.03 mbar) for 24 hours and then dissolved in 2.7 gof ethanol which has been flushed with N₂ for half an hour beforehand.The subsequent preparation of samples and the polymerization are carriedout inside a glove box under strict exclusion of oxygen. The abovemonomer mixture and the macromer solution are mixed, with the additionof 0.012 g (0.21 mmol) of Darocur®1173 and the mixture is subjected tomicrofiltration (0.45 μm filter). 180 μl of this mixture are introducedinto polypropylene molds, which are then closed with an appropriate lidof polypropylene. The molds are then irradiated with a UV-A mercury highpressure lamp in a nitrogen atmosphere in a UV oven for 5 minutes. Thelamps (5 each of the brand TLK 40W/10R, Philips) are located above andbelow the mold holder. The irradiation intensity is 14.5 mW/cm².

The polypropylene molds are then transferred to a laminar flow hood andopened. The finished lenses are released from the molds by soaking in asolvent mixture of methylene chloride and ethanol (2:3). The lenses areextracted in ethanol at room temperature in special polypropylene cagesfor 48 hours and then dried at 40° C. under 10 Pa (0.1 mbar) for 24hours. Sterilization is accomplished by autoclaving at 120° C. for 30minutes. The lenses obtained show an E modulus of 0.7 MPa, an oxygenpermeability of 96 barrer and a hardness (Shore A) of 53.

EXAMPLE B-1

Plasma Induced Surface Graft Polymerization of 2-isocyanatoethylmethacrylate on Contact Lenses (Poly-IEM 1 coating)

The substrates including two contact lenses from Example A-4 and twolenses from Example A-8 are, after extraction in isopropanol and dryingat 0.01 mbar, placed on convex glass holders (in order to expose thefront curve of lenses and to shield the back curves of the lenses fromany deposit) within the plasma reactor equipped with external ringelectrodes. The distance between the substrates and the lower rim of theplasma zone is 12 cm. The reactor is evacuated to a pressure of 0.010mbar, and held at these conditions for one hour. Then, the argon plasmagas flow rate into the plasma zone of the reactor is set to 20 sccm(standard cubic centimeters), the pressure in the reactor is adjusted to0.07 mbar and the RF generator (27.12 MHz radio frequency generator, HFAKoppold & Co., Höhenkirchen, Germany) is switched on. The plasmadischarge is maintained at a power of 170 Watts for a total period of 1minute (in order to clear and activate the substrate surfaces).Afterwards, the IEM vapor carried by an argon gas stream is introducedinto the reactor chamber from the IEM reservoir (maintained at 25° C.)at 0.15 mbar for 1 minute. After this, the following parameters for theplasma induced polymerization of IEM are chosen: Argon flow rate forplasma excitation=20 sccm, argon carrier gas flow rate for monomer (IEM)transport=10 sccm, temperature of the monomer (IEM) evaporation unit=25°C., the distance between the lower rim of the plasma zone and thesubstrates=16 cm, the pressure=0.10 mbar, and plasma power=160 W. After5 minutes of deposition, the plasma discharge is interrupted, thereactor is evacuated and maintained for 30 minutes at a pressure of0.010 mbar. The reactor is then filled with dry nitrogen gas atatmospheric pressure. The lenses are then turned over, inserted intoconcave glass holders, and the whole procedure is repeated in order tocoat the back side of the lenses.

The samples are then unloaded from the reactor and analyzed by ATR-FTIRmeasurements. Strong absorption bands at about 2270 cm⁻¹, illustrate thehigh OCN-surface functionality of the coated contact lenses.

EXAMPLE B-2

Plasma Induced Polymerization of 2-isocyanatoethyl methacrylate onContact Lenses and on Ultrafiltration Membranes (Poly-IEM 2 Coating)

The substrates including 2 lenses from Example A-4, 2 lenses fromExample A-8 and 2 pieces of polycarbonate filter membranes of a diameterof 25 mm (Poretics Corporation, Livermore, USA) are, after extraction inisopropanol, placed on a glass holder. The holder is positioned in thereactor at a distance of 16 cm from the lower edge of the plasma zone.The remaining steps are analogous to example B-1, namly:

Pretreatment: Pressure 0.010 mbar; 1 hour, argon plasma gas flow rate 20sccm; pressure in the reactor is adjusted to 0.07 mbar and the RFgenerator is switched on. The plasma discharge at 170 W (1 minute).

Coating step: Argon flow for plasma excitation=20 sccm, argon carriergas flow rate for monomer (IEM) transport=10 sccm, temperature ofmonomer (IEM) evaporation unit=25° C., the pressure=0.10 mbar, and thedistance between the lower edge of the plasma zone and the substrates=15cm. The graft polymerization is performed at a plasma power of 140 W for5 minutes. At the end of the reaction period, the previous pressure of0.010 mbar is restored and maintained for 30 minutes. The pressure isthen brought to atmospheric pressure by using dry nitrogen.

The substrates are then turned over and the whole procedure is repeatedto coat the other side of the substrates.

ATR-FTIR measurements show strong bands at about 2270 cm⁻¹, (N=C=Ogroups)

EXAMPLE B-3

Plasma Induced Polymerization of 2-isocyanatoethyl methacrylate(Poly-IEM 3 Coating)

In analogy to example B-2, the substrates including 2 lenses fromExample A-4 and 2 lenses from Example A-8 are, after extraction inisopropanol, placed on a glass holder and positioned in the plasmareactor at a distance of 15 cm from the lower edge of the plasma zone.Pretreatment is identical to example B-2. Coating step conditions:Lenses repositioned at 25 cm from the lower edge of the plasma zone. IEMplasma induced polymerization in analogy to example B-2, at 160 W (5minutes). Remaining steps identical to example B-2. Strong bands atabout 2270 cm⁻¹ (ATR-FTIR spectroscopy).

EXAMPLE B-4

Plasma Induced Polymerization of 2-isocyanatoethyl methacrylate(Poly-IEM 4 Coating)

The substrates used for this coating are: 2 lenses from Example A-4, 2lenses from Example A-8 and 2 pieces of PVP free polycarbonate membranes(Poretics Corporation, Livermore, USA) of a diameter of 25 mm.Pretreatment of the substrates in analogy to example B-3s whereinsubstrates at 15 cm from the lower edge of the plasma zone, pressure0.012 mbar (40 min.), argon plasma gas flow rate 20 sccm, pressure inthe reactor adjusted to 0.10 mbar and the RF generator is switched on(200 W for 1 minute). Coating steps : Repositioning of the substrates to20 cm from the bottom of the plasma zone. IEM plasma inducedpolymerization in analogy to example B-3, at 180 W (5 minutes), pressure0.2 mbar. At the end of the reaction period, the monomer vapor isfurther introduced in the postdischarge region for 15 minutes. Then theground pressure of 0.012 mbar is re stored and maintained for 30minutes. The remaining steps as in example B-1. Strong bands at about2270 cm⁻¹ (ATR-FTIR spectroscopy).

EXAMPLE B-5

Plasma Induced Polymerization of Glycidyl Methacrylate (Poly-GMACoating)

The substrates including 2 polycarbonate filter membranes of a diameterof 25 mm (Poretics Corporation, Livermore, USA) and 2 pieces of siliconefilm (Silastic,. Dow Chemicals) are, after extraction in isopropanol,placed on a moveable teflon holder. The holder is positioned in theplasma reactor at a distance of approximately 10 cm downstream from theedge of the visible plasma zone. After mounting samples, the system ispumped down to a pressure of 0.010 mbar, and held at these conditionsfor one hour. Then the argon plasma gas flow rate into the plasma zone of the reactor is set to 20 sccm, the pressure in the reactor is adjustedto 0.15 mbar and the RF generator is switched on. The plasma dischargeis proceeded at a power of 170 W for a total period of 1 minute. Theplasma discharge is then interrupted and GMA vapor is introduced fromthe GMA reservoir (maintained at 30° C.) into the reactor at 0.25 mbarfor 5 minutes. After this pretreatment period, the following parametersfor the plasma induced grafting of the GMA are established: Argon flowfor plasma excitation=10 sccm, argon carrier gas flow rate for monomer(GMA) transport=10 sccm, temperature of monomer (GMA) evaporationunit=35° C., the pressure=0.35 mbar, and the distance between the loweredge of the plasma zone and the substrates=16 cm. The graftpolymerization is performed at a plasma power of 150 W for 5 minutes. Atthe end of the reaction period, the GMA vapor is introduced in thepostdischarged region for a further 5 minutes. The ground pressure of0.010 mbar which is then restored and maintained for 30 minutes isbrought to atmospheric pressure by using dry nitrogen.

The substrates are then turned over and the whole procedure is repeatedto coat the other side of the substrates.

The samples are then unloaded from the reactor and analyzed by ATR-FTIRmeasurements. The absorption band at 1270 cm⁻¹ indicates the high epoxysurface functionality on all the samples.

EXAMPLE B-6

Plasma Induced Polymerization of Methacrylic Acid Anhydride (Poly-MAHCoating)

The substrates including two lenses from Example A4, and two lenses fromExample A-8 are, after extraction in isopropanol, placed on the glassholder within the plasma reactor. Pretreatment identical to example B-5,with the proviso that GMA is replaced by MAH, and substrates at 12 cm.

Coating step is identical to example B-5, with the proviso that MAHreservoir is maintained at 30° C., substrates at 16 cm and plasmapower=160 W (10 minutes). Remaining operations identical to example B-5.

ATR-FTIR analysis show bands at 1800 and 1760 cm⁻¹ (anhydride).

EXAMPLE B-7

Plasma Induced Polymerization of 4-vinyl-2,2-dimethyl Azlactone (VAL)

In analogy to the procedure disclosed in example B-2, Poreticspolycarbonate ultrafiltration membranes were treated with VAL (ISOCHEM,Vert le Petit, France). Pretreatment (step 1) parameters are ajusted to:Argon plasma gas flow 20 sscm/min.; pressure 0.085 mbar; power 520 W;time 2 min.

The parameters for the plasma polymerization (step 2) are adjusted to:Argon carrier gas flux 10 sccm/min.; temp. of VAL source evaporator −15°C.; pressure 0.2 mbar; distance of sample from plasma zone 18 cm;reaction time 5 min.; power 375 W; pulsed plasma, frequencycorresponding to 10:30 μsec (on:off time).

ATR-FTIR measurements show absorption bands at 1820 and 1770 cm⁻¹(azlactone)

EXAMPLE B-8

In analogy to the procedure of example B-7, contact lenses of exampleA-4 were coated.

EXAMPLE C-1

Determination of N═C═O and azlactone group concentration on modifiedsurfaces by the reaction with the spin label molecule4-amino-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-amino-TEMPO). Ten IEMplasma modified contact lens and ultrafiltration membranes (Poretics™, apolycarbonate material) samples from the examples indicated infra aresoaked in a solution of 0.05 g of 4-amino-TEMPO (Fluka 09465) dissolvedin a mixture of 1 ml of water and 4 ml of isopropanol. The isocyanategroups on the substrate surfaces are reacted with the spin labelcompound at 25° C. for 4 hours. The substrates are then washed 3 timesin the same mixture solvent (i-propanol/water 4:1) and extracted for 12hours in isopropanol. After drying at a reduced pressure of 0.010 mbar,the substrates are analyzed by ESR spectroscopy.

Concentration of spin label molecules on subtrate surfaces: Substratefrom Coating from Concentration · Example Example 10⁻⁹ Mol spin/cm²contact lenses A-4 B-1 4.09 A-8 B-1 2.65 A-4 B-2 4.96 A-8 B-2 2.65 A-4B-3 6.99 A-8 B-3 4.18 A-4 B-4 7.57 A-8 B-4 7.66 A-4 B-8 2.20 membranesPoretics B-4 10.76 Poretics B-2 3.89 Poretics B-7 1.90

EXAMPLE C-2

Coupling reaction of isocyanate functionalized substrates with BovineSerum Albumin. Three lenses from Example A-4 and 3 contact lenses fromExample A-8 are surface modified with IEM according to the proceduredescribed in Example B-4. The isocyanate functionalized contact lensesare then reacted with Bovine Serum Albumin (BSA) by immersing each lensin 3 ml aqueous solution containing 30 mg BSA at 25° C. for 16 hours.Following the albumin treatment, the lenses are extracted for 12 hourswith ultra pure water to remove unreacted albumin. After this, thelenses are analyzed by ATR FTIR and contact angle measurements.

Contact Lenses from Example: A-4 A-8 Contact angles Advancing angle(Adv.) 26 49 Receding angle (Rec.) 19 43 Contact angle Hysteresis(Hyster.) 7 6

The FTIR-ATR spectra confirm the complete conversion of the OCN-groupsdue to the absence of an absorption at 2270 cm⁻¹.

EXAMPLES C-3-C-7

Coupling reactions of isocyanate functionalized substrates with otherproteins. Substrates from Example A-4 and substrates from Example A-8are surface functionalized with isocyanate groups as described inExample B-4. The functionalized substrates are then soaked in 1% aqueoussolutions of various proteins to provide the coupling reactions inaccordance with the procedure in Example C-2. After extraction in HPLCwater the substrate surfaces are analyzed by ATR FTIR spectroscopy andcontact angle measurements.

Contact angles on substrates modified by plasma induced polymerizationand subsequent reactions with proteins (Examples C-3-C-7) are shown inTable 1.

TABLE 1 Substrate Coupling* Ex- from Contact angle [°] with ampleExample No. Protein used Adv/Rec./Hyster. OCN groups C-3 A-4 Hirudin21/11/14 quantitative A-8 (Ciba-Geigy) 38/25/13 quantitative C-4 A-4Collagen III, 43/28/15 quantitative A-8 from calf 53/41/12 quantitativeskin (Sigma) C-5 A-4 Mucin II, 19/12/7 quantitative A-8 from porcine23/14/9 quantitative stomach (Sigma) C-6 A-4 Mucin I-S, 57/19/38quantitative A-8 from bovine 52/28/24 quantitative submaxillary glandsC-7 A-4 Elastin 53/33/20 quantitative A-8 bovine neck 55/31/24quantitative (Fluka) *confirmed by FTIR-ATR spectroscopy

EXAMPLE C-8

Coupling reaction of isocyanate functionalized substrates with JeffamineED 2001. Two contact lenses from Example A-4 and 2 contact lenses fromExample A-8 are isocyanate functionalized as in Example B-4. Each lensis then individually soaked in 3 ml aqueous solution of Jeffamine ED2001 (Texaco, USA) having a concentration of 10 mg Jeffamine/1 ml water.The coupling reaction is allowed to proceed overnight (16 hours) at roomtemperature. The substrates are then carefully rinsed with distilledwater, extracted for 12 hours with ultra pure water and analyzed byATR-FTIR and contact angle measurements.

Substrate from Example: A4 (B-4) A-8 (B-4) Contact angles: 53/28/2553/20/33 Adv./Rec./Hyster.:

EXAMPLES C-9-C-11

Coupling reactions of isocyanate functionalized substrates with otherpolymers. The process described in Example C-8 is repeated for couplingreactions of isocyanate functionalized substrates with otheramino-containing polymers listed infra. Contact angles measured on themodified substrates are summarized in Table 2.

TABLE 2 Substrate from Contact angle [°] Example Example Polymer usedAdv./Rec./Hyster. C-9 A-4 Amino-terminated 36/4/32 A-8 PVP (Example A-1)25/7/18 C-10 A-4 PVA with pendant 27/21/6 A-8 amino groups (Example A-2)44/38/6 C-11 A-4 Polyethyleneimine 73/62/11 A-8 (Fluka) 66/51/15

EXAMPLE C-12 AND C-13

The process described in Example C-8 is repeated for coupling reactionsof isocyanate functionalized substrates with amino-cyclodextrin (exampleA-6) and aminooctyl-lactobionolactone-amide (example A-5) respectively.Contact angles measured on the modified substrates are summarized below.

Substrate from Example: A-4 A-8 Contact angles (example A-6): 73/38/3578/40/38 Adv./Rec./Hyster.: Contact angles (example A-5): 84/42/4279/41/38 Adv./Rec./Hyster.:

EXAMPLE C-14

Determination of glycidyl and anhydride group concentration with4-amino-TEMPO. Two plasma modified substrates from Examples B-5 and 2plasma modified substrates from Example B-6 are soaked in a solution of0.05 g of 4-amino-TEMPO dissolved in a mixture of 1 ml of water and 4 mlof isopropanol. The reactive groups on the substrate surfaces arereacted with spin label molecules at 25° C. for 4 hours. The substratesare then washed 3 times in the same solvent mixture (i-propanol/water4:1) and extracted for 12 hours in isopropanol. After drying at areduced pressure of 0.010 mbar, the substrates are analyzed by ESRspectroscopy, upon which the concentration of spin label molecules isdetermined on lens surfaces.

Concentration · Substrate from example Coating from example 10⁻⁹ Molspin/cm² Silastic Film B-5 2.45 Poretics membrane B-5 2.60 A-4 contactlens B-6 7.52 A-8 contact lens B-6 4.32

EXAMPLE C-15

Coupling reaction of glycidyl and anhydride functionalized substrates. 2plasma modified substrates from Example B-5 and 2 plasma modifiedsubstrates from Example B-6 are separately soaked in a solution of 0.1 gof Jeffamine ED 2001 dissolved in 5 ml of acetonitrile. The reaction iscarried out at 25° C. for 4 hours. Then the substrates are first washedand then extracted in acetonitrile for 12 hours. After drying at areduced pressure of 0.010 mbar for 3 hours, the substrates are analyzedby ATR FTIR and contact angle measurements. Contact angles measured onthe modified substrates are summarized below:

A-4 A-8 Poretics ™ Silastic ™ contact contact Substrate from membranefilm lens lens Example: B-5 B-5 B-6 B-6 Contact angles: 69/31/3874/29/45 77/44/33 79/31/48 Adv./Rec./Hyster.: Silastic ™, silicon film(Dow Chemicals)

EXAMPLE C-16-C-18

Coupling reaction of azlactone functionalized substrates. Lensesobtained from example B-8 are treated with 5% wt. aqueous solutions ofamino-functional reagents indicated infra for 3 hrs at room temperature.Work up in accordance to example C-8.

Contact Angles Example “Amino”-Reagent Adv./Rec./Hyster.: C-16Polyethylene-imine, MW 60'000 73/48/25 Aldrich C-17 Jeffamine 2005(Texaco) 69/58/11 C-18 Diamino-polyethylene-glycol 41/29/12 MW 600(Fluka) Comparative None 103/79/24 (Uncoated lens of example A-4)

EXAMPLE C-19

284 mg of the oligopeptide H(Gly-NLeu-Pro)₉-NH₂.TFA (15 H₂O) aredissolved in 5 ml water. Adjusting the pH to 7.4 by addition of 0.1 NNaOH. Ethanol (0.3 ml) is added and the solution is filtered through a0.22 μm membrane. This clear and sterile solution is used for treatingthe substrates of example B-7, wherein the treatment process is inanalogy to example C-2. After this, the substrates are analyzed byATR-FTIR.

EXAMPLE C-20

In analogy to example C-19, two substrates of example B-7 are treated at5° C. with an aqueous solution of bovine collagen for 16 hrs. The bovinesolution is prepared from 5 ml Vitrogen 100™ (Collagen BiomaterialsInc., Palo Alto Calif.) by adding 0.625 ml phosphate buffered saline,0.625 ml 0.1 N NaOH and 3 drops 0.1 N HCl. Again, the substrates areanalyzed by ATR-FTIR.

What is claimed is:
 1. A method of preparing an article comprising asubstrate with a polymer coating carrying reactive groups on itssurface, wherein said polymeric coating comprises repeating unitsderived from a polymerizable unsaturated compound carrying a reactivegroup selected from the group consisting of isocyanato, isothiocyanato,glycidyl, anhydride, azlactone and lactone groups, wherein in saidcoating the concentration of said reactive groups is, based on spinlabel determination by ESR spectroscopy, in a range of 0.2-20·10−9 Molspin/cm2, wherein said coating is obtained by carrying out an after-glowplasma-induced polymerization of a polymerizable unsaturated compoundcarrying a reactive group selected from the group consisting ofisocyanato, isothiocyanato, glycidyl, anhydride, azlactone and lactonegroups on a substrate wherein the substrate is positioned at a distanceof 4 to 40 cm and an inlet for said polymerizable unsaturated compoundat a distance of 3 to 35 cm downstream outside of a plasma zone.
 2. Amethod according to claim 1, wherein the plasma-induced polymerizationis induced by a direct current (DC), a radio frequency (RF) or amicrowave (MV) plasma.
 3. A method according to claim 2, wherein theplasma-induced polymerization is induced by a RF plasma with inductivecoupling.
 4. A method according to claim 2, wherein the radio frequencyis 13.56 or 27.12 MHz.
 5. A method according to claim 1, wherein theplasma-induced polymerization is induced by a pulsed plasma.
 6. A methodaccording to claim 1, wherein the substrate is positioned at a distanceof 8 to 30 cm downstream from the plasma zone.
 7. A method according toclaim 1 wherein the inlet is positioned at a distance of 6 to 25 cmdownstream from the plasma zone.
 8. A method according to claim 1,wherein the article is an ophthalmic device for vision correction,wherein the plasma-induced polymerization is carried out in the presenceof the substrate that carries a removable patterned screen as a mask forthe generation of imaged surfaces.